3D Diaries Part 1

Bob Pank#

Author: Bob Pank#

Published 1st June 2010

Believe it!

Welcome to 3D Diaries, TV-Bay’s own monthly column dedicated to 3D. Each month will feature an aspect of the 3D chain from scene to screen – all areas are affected in some way or another, so there’s plenty to talk about! But this would be meaningless if you are not a 3D believer, so this month I’ve shown why 3D is now here to stay.

At NAB everyone who was anyone had something to offer for 3D. It’s the ‘next big thing’. You could see 3D images everywhere, some live and some not. Obviously the television industry’s equipment manufacturers are keen to supply this new area. After all it requires two channels of pretty much everything so this could be a boost for business – if it proves popular.

Why S-3D now?

There are few with two functional eyeballs who would not welcome the chance to see video and film material as 3D rather than the current (or is it now old?) 2D imagery. Well, what the industry is now buzzing with is not really 3D; you cannot walk around an object on the screen. This is stereoscopic 3D, or S-3D for short. It is intended to present two streams of moving images one seen by the left eye only; the other is for the right eye only. Generally these are shot with two cameras with their lens axes horizontally spaced by the same distance as our eyes – the interocular distance. (In the USA they sometimes refer to ‘interaxial distance’ between two camera lenses.)

The idea is not new, through the 20th Century various films, often horrors, were made in S-3D. Far too often they left the audience with a horrible headache. As a result 3D was later only attempted for shorter presentations, such as theme parks. The trouble with S-3D is that it’s trying to fool our highly developed visual cortex into interpreting what are eyes see as 3D. Defects in the show make it harder, or impossible for our brains to work out what’s going on – hence the headache.

To maintain the illusion requires great accuracy to be maintained all the way through from scene to screen. For many reasons film couldn’t hack it. Even if the very expensive and drawn out post processing to correct for the differences between the two cameras and their film was good enough, the projection was a nightmare. It required the images of two projectors to be perfectly registered over each other and the left and right film to be kept on perfect sync. Random artefacts such as scratches and blobs did not help to maintain the illusion. Then, when the film broke, a frame or so would be missing in the repaired footage and left-right sync was lost. Further on, the inevitable film weave crept in as the sprocket holes widened with every passage of the film through the gate. A little side-to-side weave can be tolerated but vertical displacements, not often seen in nature, are instant headache material.

Enter digital; no scratches, blotches, sparkles or weave and there are established ways to keep two players always in sync. Add to that nifty live image processing to ease out those left-and-right camera differences and the S-3D proposition looks much more interesting. Indeed, this is why the old 3D horrors are now, or at least should be, a thing of the past. Digital S-3D has the technology to do well enough to avoid headaches and let the audience revel in the third dimension.

Of course the movie industry is leading the move to S-3D. Indeed they see 3D as the digital bonus – it pulls in audiences, spoils bootlegging and they can charge more. Furthermore, you can’t see this at home – yet. S-3D digital cinema can be very easy to present as it can be run from one player and displayed by one projector showing left and right images (no fiddly registration) sequentially. So, even local fleapits equipped with digital could show glorious headache-free S-3D.

S-3D for ever

The S-3D we can now see in ‘selected’ cinemas generally gets a very good reception. It’s not perfect and never will be but it can manage to maintain the illusion. Movie studios are continuing to ramp up the proportion of 3D projects against 2D only.

There is already intense interest from some TV channels who are keen to get 3D to their viewers. It seems that the World Cup footy will not be seen live in 3D in the UK, but that does not mean 3D TV is not happening. At NAB there were screens showing live 3D coverage of the US Open golf. In the UK Sky is pioneering 3D TV, showing live events in 1,500 pubs. Interestingly this live operation is, perhaps, the most difficult to get right, as all 3D aberrations must be corrected live – and that’s no mean feat.

There are plenty of hurdles yet to be crossed and traps to steer around on the way but digital S-3D has already wowed plenty of audiences – more than enough to warrant moving the technology forward on a broad front. With the prospect of ‘true’ 3D nowhere over the horizon, S-3D will prevail for many decades yet. We are just at the beginning.

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